Vision is active. It is a dynamic process, resulting from an interaction between context, perceptual learning and top-down influences. All cortical and thalamic levels of sensory processing are subject to powerful top-down influences, the shaping of lower level processes by higher order, more complex information and cognitive states. There is an expanding view of the kind of information that is conveyed in a top-down fashion, including attention, expectation, and perceptual task. As a consequence every cortical area acts as an adaptive processor, undergoing continuing cycles of state change and functional switching, with earlier states influencing the way in which the bottom up sensory information is interpreted in subsequent states. In this proposal we will explore the functional role of top-down influences, study the mechanisms by which these influences are exerted, and determine how different visual cortical areas participate in top-down interactions. We will continue our studies on perceptual learning, determining how learning object shape affects the functional properties of neurons at different stages in the visual pathway. We will study the role of early visual areas in intermediate level vision, the parsing of visual images into objects and background, contour integration, and the representation of object shape. The experimental approach will involve recording from single neurons and neuronal ensembles while animals are performing visual discrimination tasks, which enables us to determine how learning and perceptual task influences the function of different cortical areas, the circuit mechanism of this process, and the way in which these areas analyze visual images.